Cannot get it to work after installation

I loaded the folder on my server and the requirements test passes, but if I insert a link through the interface it returns me:

"
Fatal error: Uncaught Error: Call to undefined function Masterminds\HTML5\Parser\mb_decode_numericentity() in /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5/Parser/CharacterReference.php:53 Stack trace: #0 /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5/Parser/Tokenizer.php(1075): Masterminds\HTML5\Parser\CharacterReference::lookupDecimal(‘44’) #1 /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5/Parser/Tokenizer.php(213): Masterminds\HTML5\Parser\Tokenizer->decodeCharacterReference() #2 /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5/Parser/Tokenizer.php(153): Masterminds\HTML5\Parser\Tokenizer->rcdata() #3 /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5/Parser/Tokenizer.php(131): Masterminds\HTML5\Parser\Tokenizer->characterData() #4 /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5/Parser/Tokenizer.php(87): Masterminds\HTML5\Parser\Tokenizer->consumeData() #5 /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5.php(174): Masterminds\HTML5\Parser\Token in /var/www/html/full-text-rss-3.9.1/libraries/html5php/HTML5/Parser/CharacterReference.php on line 53
"

Any hint of how can I move on?

Hi there, can you send us a link (URL) to the location where you installed it so we can have a look?